When it comes to diagnosing depression in teens, differentiating mental illness from normal mood swings can be difficult. But it can be a crucial diagnosis, given that untreated depression in youth makes them more vulnerable to later substance abuse, social maladjustment, physical illness and suicide.

“Depression in adolescents affects basically every component of their thinking and makes everything very difficult psychologically and socially,” says Eva Redei, a professor of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine.

Currently, a depression diagnosis in teens relies on their descriptions of symptoms and their physician’s subjective observations. But now a new study suggests there may be a surer, more objective way: a blood test that identifies major depression by looking for a specific set of genetic markers in the blood. The breakthrough could lead to earlier diagnoses that may not only allow for better individualized treatment but also help to lessen the stigma associated with mental illness.

“The idea is that if you have an objective measure that is similar to any other lab test, it will bring mental illness into the same arena as other illnesses,” says lead researcher Redei.

The stigma attached to depression and counseling is one of the reasons only 25% of depressed teenagers go treated, says Redei. “The test could decrease the stigma since no one could say, ‘Just get yourself together.’ There is a set and defined imbalance shown in the test. Patients will feel less ostracized and will be more likely to see a physician,” she says.

In the study, Redei and her team looked at teens from the Research Institute of Nationwide Children’s Hospital in Columbus, Ohio. They analyzed 14 teens with major depression and 14 nondepressed teens all ages 15 to 19. They tested the teens’ blood for 26 genetic markers of major depression that Redei had previously identified in studies with lab rats. They found that 11 markers showed up in depressed teens but not in their healthy peers. Not only that, 18 of the markers could also distinguish teens with depression alone or depression with other anxiety disorders.

“It’s similar to cholesterol testing. If the levels are not within the normal range, they are flagged,” says Redei. The genetic markers came from decades of research on severely anxious and depressed rats. The markers identified in the rats’ blood were compared with the markers found in the humans.

Notably, the study size was very small, and further and more extensive research is still needed. “This is really the beginning,” says Redei. “The fact that we were able to diagnose depression in this small study is very promising.”

The findings carry exciting potential, but Dr. Adelaide Robb, a child-and-adolescent psychiatrist at the Children’s National Medical Center in Washington, D.C., stresses that it’s still too early to consider the “problem solved.” “Taking something from an animal model and saying it means something in people is making a big leap,” she says. “A finding among 14 is not the same as saying something is present in 1,000 people.”

She acknowledges it is a fine first start that gives researchers an idea of where to look for further blood-test development. “If we could identify several subtypes of depression, we could, hopefully, target treatments for subsections of people with certain abnormal neurochemicals,” she says. “But parents still need to look at this critically. I don’t want to see people trying to get this done when you can still be diagnosed with a clinical interview.”